Filling Level Radar with Variable Transmitting Power

ABSTRACT

A level measuring instrument has a variable transmitting power for measuring a filling level in a tank. The level measuring instrument includes a generator unit selectively generating different transmitting powers. The generator unit is controlled so that the transmitting power is respectively adapted to the corresponding environmental conditions. For this purpose, the generator unit has for instance two different oscillators, which are driven selectively.

REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Patent Application Ser. No. 60/740,747 filed Nov. 30, 2005,and German Patent Application Serial No. DE 10 2005 057 094.1 filed Nov.30, 2005, the disclosures of which are hereby incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to level measuring. In particular, this inventionrelates to a filling level measuring instrument with variabletransmitting power for measuring a filling level in a tank, a generatorunit and a controller for generating variable transmitting power, and amethod for measuring a filling level in a tank.

TECHNICAL BACKGROUND

Known filling level measuring instruments for contactless measuring havean antenna, which transmits or receives signals (radar or microwave,ultrasound) in order to determine the filling level of a medium, e.g. ina filling material container. The antenna of such a level measuringinstrument is then arranged for instance inside a container.

The quality of the measuring signals received at level measuring with alevel measuring instrument is largely dependent on the quality of thetransmitting-/receiving unit. In particular, the strength or amplitudeof the receive signal is critical therein. If the amplitude is small,e.g. because the measuring signal on its way from the transmitter to thefilling material and back again was strongly attenuated, the quality ofthe gating and thus the measuring result deteriorates. On the otherhand, if the amplitude of the signal received is too high, the receivingunit will overload. This may result in a measuring error.

SUMMARY OF THE INVENTION

According to a sample embodiment of this invention, a level measuringinstrument with variable transmitting power for measuring a fillinglevel in a tank is provided, the level measuring instrument comprising agenerator unit for generating a transmit signal and a controller forcontrolling the generator unit, wherein the generator unit is configuredfor selectively generating a first transmitting power of the transmitsignal or a second transmitting power of the transmit signal.

E.g., the generator unit according to this sample embodiment of thisinvention may always generate a transmit signal of the firsttransmitting power, when environmental conditions are relatively good,i.e. small losses of the transmit signal on its way through a fillingmaterial container back to the level measuring instrument may beanticipated. In this case, the transmitting power is then setcorrespondingly low. On the other hand, under more difficultenvironmental conditions, e.g. if the filling material is relatively faraway from the level measuring instrument, or in case of an atmospherewith relatively high absorption, the generator unit may set thetransmitting power of the transmit signal correspondingly high(according to the second transmitting power). This may ensure that evenunder more difficult conditions, a sufficiently strong receive signalcan make its way back to the detector of the level measuring instrument,so that the quality of the measuring result is maintained.

In other words, this may be done by adapting the transmitting power sothat the levels of the receive signals are optimal, even under widelyvarying environmental conditions.

According to another sample embodiment of this invention, the generatorunit comprises a first oscillator for generating a first oscillatorsignal and a second oscillator for generating a second oscillatorsignal, wherein the controller is configured for selectively driving thefirst oscillator or the second oscillator.

Depending on whether the first oscillator signal or the secondoscillator signal is actually generated, either a transmit signal with afirst (lower) transmitting power, or a transmit signal with a second(higher) transmitting power, is output.

This may be done e.g. in that both oscillators deliver different powers(i.e. for instance they have different dimensions), or in that theoutput power of the second oscillator is amplified more strongly thanthe output power of the first oscillator, or else in that the outputpower of the first oscillator is attenuated (wherein both oscillatorscan then e.g. be configured in the same way).

According to another sample embodiment of this invention, the levelmeasuring instrument comprises a reference signal retrieval point (tap)from the first oscillator signal or the second oscillator signal.

With level measuring instruments such a tap may be used e.g. forextracting a reference signal according to the pulse-running timeprinciple before the transmit signal is delivered to the antenna andleaves the level measuring instrument. This extracted signal maythereafter be used to determine the running time of the transmit signal.

According to another sample embodiment of this invention, the levelmeasuring instrument further comprises an attenuation element forsetting attenuation of the first oscillator signal.

Thus, e g. both oscillators may be configured in the same way, with theoutput signal of the first oscillator being attenuated accordingly, sothat eventually two different transmitting powers are provided. Such anattenuation clement may be integrated in the waveguide between the firstoscillator and the reference signal extraction point.

According to another sample embodiment of this invention, theattenuation element is configured as an attenuation mat to be adhered toa substrate.

Thus, the attenuation element is not integrated into the line, butrather mounted near the line. By modifying the size, thickness, oranother parameter of the attenuation mat, the attenuation factor may beset adequately, depending on the requirements on the level measuringinstrument.

According to another sample embodiment of this invention, theattenuation element has variable, controllable attenuation, wherein thecontroller is configured for controlling the attenuation element.

Thus, according to this sample embodiment of this invention, theattenuation may be set individually according to the requirements. Inthis case may be possible for instance to configure the generator unitwith one oscillator only, the output power of which is attenuatedadequately if the power of the measuring signal is too high.

Of course, in this case, too, it may be possible to provide twooscillators, with both oscillators being configured e.g. in the sameway, i.e. imitating the same power.

According to another sample embodiment of this invention, the levelmeasuring instrument further has a transmission amplifier for settingamplification of the second oscillator signal.

Here again, e.g. a total of one oscillator only is provided, the outputpower of which is amplified adequately, or not amplified, depending onthe environmental conditions.

Of course, in his case, too, it may be possible to provide two identicaloscillators, with the power of one of them being amplified and, inaddition, the power of the other one may be attenuated e.g. by anattenuation mat so that the difference in power between both powersfurther increases.

According to another sample embodiment of this invention, the levelmeasuring instrument further comprises a directional coupler with afirst input, a second input, a first output and a second output, whereinthe first input of the directional coupler is connected to the firstoscillator, and the second input of the directional coupler is connectedto the second oscillator. In addition, the first output of thedirectional coupler is configured as a retrieval point of the referencesignal, and the second output of the directional coupler is configuredfor outputting the transmit signal. The directional coupler isadditionally configured for attenuating a signal, which is fed at thefirst input and output at the second output.

E.g. a signal, which is entered at the first input and output at thefirst output, may be attenuated much less strongly. Also, a signal,which is entered at the second input and output at the second output,may be attenuated much less strongly, whereas such a signal entered atthe second input, if it is output at the first output, is stronglyattenuated.

In this way, the level difference between both oscillator signals may befurther increased. Thereby, the attenuation mat or the amplifier maypossibly be omitted completely.

According to another sample embodiment of this invention, thedirectional coupler is configured as a symmetric or asymmetric hybridcoupler.

Such a symmetric or asymmetric hybrid coupler may be integrated easilyinto the circuit.

According to another sample embodiment of this invention, the levelmeasuring instrument is configured as a pulse radar system. The firstand second oscillator signals are electromagnetic pulses.

Of course, the oscillators may also be configured so as to emitultrasonic waves. In this case, the level measuring instrument is anultrasonic measuring instrument.

According to another sample embodiment of this invention, the levelmeasuring instrument further comprises a receiving unit, wherein thecontroller is coupled with the receiving unit, and wherein thecontroller is configured for controlling the generator unit so that thefirst transmitting power is generated when the strength of the receivesignal exceeds a threshold value.

In this way, test measurements may be carried out in order to find outwhether the power received is within an acceptable range. If the signalstrength received exceeds an upper threshold value, it may be possiblee.g. to switch from the second oscillator to the first oscillator, or itmay be possible to increase attenuation so that the power of thetransmit signal decreases. On the other hand, e.g. if the receive signalhas a strength, which lies below a second threshold value, the power ofthe transmit signal may be increased by adequately driving the generatorunit. E.g., for this purpose, switching from the first oscillator to thesecond oscillator takes place, or attenuation is decreased.

Of course, it may be possible to provide further additional oscillatorsand possibly corresponding attenuation elements or amplifiers, e.g. inorder to dispose of more than two (discrete) transmitting powers.

According to another sample embodiment of this invention, receipt,determination of power, and comparison with the threshold value of thereceive signals are performed automatically.

E.g., such signal strength measurements may be performed automaticallyat regular intervals. Thus, a mostly continuous regulation of thetransmitting power may take place, which is respectively adapted toexternal conditions,

If the transmitting power can be varied continuously (not in discretesteps), then it may be attempted first of all to still detect even smallreceive signals by means of as much transmitting power as possible. Dueto an evaluation of the useful signal strength, the transmitting powermay then be reduced until the receiving level is in the optimal range ofthe receiver.

According to another sample embodiment of this invention, a generatorunit for generating different transmitting powers of a transmit signalfor measuring a filling level is provided.

According to another sample embodiment of this invention, a method formeasuring a filling level in a tank is provided, wherein a generatorunit for selectively generating a first transmitting power or a secondtransmitting power of a transmit signal is driven, and the transmitsignal is generated accordingly, selectively with either the firsttransmitting power or the second transmitting power.

Thereby a method is provided, by which the transmitting power may beadapted so that the receive signals are respectively optimized.

According to another sample embodiment of this invention, the methodfurther comprises receiving a receive signal, determining a power of thereceive signal, and driving the generator unit so as to generate thefirst transmitting power if the signal strength of the receive signalexceeds a threshold value.

According to another sample embodiment of this invention, the generatorunit comprises a first oscillator for generating a first oscillatorsignal and a second oscillator for generating a second oscillatorsignal.

According to another sample embodiment of this invention, the generatorunit controls a variable attenuation stage or a variable amplificationstage depending on a defined signal strength of the receive signal,wherein only one oscillator for generating the transmitting power isimplemented.

According to another sample embodiment of this invention, the generatorunit controls the variable attenuation stage or the variableamplification stage independently from the signal strength of thereceive signal.

Further sample embodiments, objects, and advantages of the invention areapparent from the subclaims.

Hereafter, with reference to the figures, preferred sample embodimentsof this invention will be described.

SHORT DESCRIPTION OF THE FIGURES

FIG. 1 shows a schematic cross-sectional view of a level measuringinstrument according to a sample embodiment of this invention.

FIG. 2 shows a schematic block diagram of a generator unit and acontroller according to a sample embodiment of this invention.

FIG. 3 shows a schematic block diagram of a generator unit and acontroller according to another sample embodiment of this invention.

FIG. 4 shows a schematic view of a directional coupler according to asample embodiment of this invention.

FIG. 5 shows a schematic block diagram of a generator unit and acontroller according to another sample embodiment of this invention.

FIG. 6 shows a schematic block diagram of a generator unit and acontroller according to another sample embodiment of this invention.

The views in the figures are schematic and not to scale.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the following description of the figures, the same reference symbolswill be used for identical or similar items.

FIG. 1 shows a schematic cross-sectional view of a filling level radar100 according to a sample embodiment of this invention. The fillinglevel radar 100 has an antenna 109 and a housing 108, which accommodatesthe generator unit 113, the controller 103, and the receiving unit 116.In the generator unit 113, transmit signals 107 are generated, which aredelivered to the antenna 109, and are then emitted as transmit signals110 towards the filling material 112. The transmit signals 110 are thenreflected at the filling material surface 112, and received as reflectedsignals 111 by the antenna 109, and thereafter supplied as signals 117to the receiving unit 116, and correspondingly evaluated therein.

E.g., the generated transmit signals 107 are electromagnetic highfrequency signals, as they are typically used for radar measurements. Inthis case, frequencies lie in e.g. in the gigahertz range, in particularin the range between 5 GHz and 100 GHz.

Of course, the level measuring instrument represented in FIG. 1 may alsobe configured as an ultrasonic instrument. In this case, the generatedsignals are not electromagnetic signals, but sound signals, which aregenerated e.g. by the oscillators 101, 102.

In the sample embodiment represented in FIG. 1, the generator unit 113comprises two oscillators 101, 102, which respectively generate oneoscillator signal 114, 115. The oscillator signal 114 generated by thefirst oscillator unit 101 is attenuated via an attenuation element 105.Both signals 114 (via attenuation element 105), and 115 then run into adirectional coupler 106, wherein a reference signal 104 is tapped orderived. The output signal 107 is then forwarded to the antenna.

As the dynamic range of a conventional pulse radar system is limitedboth in the HF and receiving range, according to the invention, fordifferent applications, different transmitting levels are used (which inthe case of FIG. 1 are generated by the first oscillator 101 togetherwith the attenuation element 105 or by the second oscillator 102).

The attenuation element 105 is e.g. configured as an attenuation mat,which may be dimensioned adequately.

However, the attenuation element 105 can also be configured as avariable attenuation element, which is driven adequately by thecontroller 103 so that the attenuation may be modified automaticallyduring measuring.

The controller 103 is connected to the two oscillators 101, 102 so as tobe able to drive both oscillators 101, 102 individually. Thus, the firstoscillator 101 is driven for instance by the controller 103 if lowtransmitting power is desired. The second oscillator 102 is driven forinstance by the controller 103 if high transmitting power is desired.

FIG. 2 shows a schematic block diagram of a generator unit 113 and acontroller 103 according to another sample embodiment of this invention.In the transmit path 115 of the second oscillator 102, an amplifierelement 201 is provided, which is meant for amplifying the secondoscillator signal 115. This amplifier element 201 can also be connectedto the controller 103 so that the amplification may be controlled.

FIG. 3 shows a schematic block diagram of a generator unit 113 and acontroller 103 according to another sample embodiment of this invention.Herein, the two oscillators 101, 102 are dimensioned differently, i.e.they have different output powers. This can be done e.g. in that theoscillators 101, 102 have different operating states, such as e.g.different gate bias voltages (for FET oscillators) or differentoperating voltages. Such oscillators can be configured e.g. as GaAsfield effect transistor oscillators. However, other oscillators areequally possible, in particular (in case of an ultrasonic levelmeasuring instrument) adequate acoustic oscillators.

In addition, switches 301, 302 are provided, which may be switchedadequately by the controller 103 so that according to requirements,either one oscillator 101 or the other oscillator 102 is connected.

FIG. 4 shows a schematic view of a directional coupler 106 according toa sample embodiment of this invention. This directional coupler 106 isconfigured e.g. as an asymmetric hybrid coupler, and can be integratedinto the circuit 113.

The incoming signal 114 of the first oscillator 101 travels through thedirectional coupler e.g. with a relatively low attenuation of −1 dB inorder to be then picked up at the first output 104 (the tap for thereference signal). This is represented by reference symbol 401.

However, if the input signal 114 of the first oscillator 101 is pickedup at the second output (as transmit signal 107), then it is attenuatedby the directional coupler on its way 402 by e.g. −10 dB. Of course,higher or lower attenuation can also be performed according to thedesign of the directional coupler 106 (this is true for the case of anasymmetric hybrid coupler). For symmetric hybrid couplers, attenuationsare the same in both signal directions (401 and 402).

Similarly, the signal 115 coming from the second oscillator 102 isattenuated on its way through the directional coupler towards theantenna by only −1 dB (represented by reference symbol 403). However, ifthe second signal 115 travels transversely to the directional coupleralong the arrow 404 in order to be carried to the output 104 (tap), thenit is accordingly attenuated more strongly, e.g. by −10 dB.

I.e., the controller 103 selectively drives either the first oscillator101 or the second oscillator 102. The attenuation for one of bothoscillator paths can be generated by means of an adhesive attenuationmat. It may also be possible to provide equalization of bothoscillators. This equalization is performed by varying the supplyvoltage or the operating state of the oscillator. Thereby, leveldifferences of both oscillators may be obtained. Also, a downstreamamplifier (between hybrid coupler and antenna) may be provided (notshown in the figures), which is active at all times.

By using an asymmetric hybrid coupler 106, it is possible to furtherincrease the level difference between both oscillators 101, 102.Thereby, the attenuation mat or the attenuation element 105 may possiblybe omitted completely or at least configured considerably smaller.

FIG. 5 shows another schematic block diagram of a generator unit 113with the controller 103 according to another sample embodiment of thisinvention. As may be seen in FIG. 5, the generator unit 113 has threedifferent separate oscillators 101, 102, 501, wherein the thirdoscillator 501 is designed to deliver a higher transmitting power thanthe first two oscillators 101, 102.

All three oscillators 101, 102, 501 are driven by the controller 103.The output signal of the first oscillator 102 is attenuated by theattenuation element 105 before it is supplied to the directional coupler106. The attenuation can be set by the controller 103 via the line 506.The second oscillator signal 115 of the second oscillator 102 is alsosupplied to the directional coupler 106. The directional coupler 106 nowensures that tapping 104 of a reference signal from the first oscillatorsignal or the second oscillator signal (depending on driving, i.e.depending on whether the first oscillator or the second oscillator isactivated) is performed. In addition, the directional coupler 106ensures that an output signal 505 is generated, which is e.g. onlyslightly attenuated.

This output signal 505 is supplied to a second directional coupler 503.In addition, the second directional coupler 503 is supplied with a thirdoscillator signal 502 by the third oscillator 501. This third oscillatorsignal 502 has higher power than output signal 505.

The second directional coupler 503 may now ensure that on the one hand,a transmit signal 107 is output, which is only slightly attenuated, andthat on the other hand, a second tapping 504 is performed, as a secondreference signal.

According to another sample embodiment of this invention, tap 104 is notprovided, but only tap 504.

In the sample embodiment shown in FIG. 5, it may thus be possible togenerate three different output transmitting powers of the transmitsignal 107, depending on which of the three oscillators 101, 102, 501 isdriven by the controller 103. A large dynamic range may thus be providedso that the transmitting power may respectively be adapted to thecorresponding application. Of course, it may also be possible tointegrate further oscillators into the generator unit 113 so thatfurther output powers may be generated. Thereby, the dynamic range ofthe filling level measuring device may further be increased.

In the sample embodiment shown in FIG. 6, only one transmittingoscillator 101 is made, which generates different transmitting levels107 by means of a variable attenuation/amplification unit 601. Thevariable attenuation/amplification unit 601 is then driven by thecontroller 103. From the receiving unit 116, it receives adequateinformation in order to increase or decrease the transmit level. Thevariable attenuation/amplification unit 601 may be configured indifferent ways. E.g. as an amplifier or as a variable attenuationmember.

Of course, the various sample embodiments represented may be combinedwith each other at will.

The configuration of the invention is not limited to the preferredembodiments represented in the figures. Instead, a plurality of variantscan be envisaged using the represented solution and the principleaccording to the invention even for embodiments of a basically differentkind.

Additionally, it is to be noted that “comprising” does not exclude anyother items or steps, and that “a” or “an” do not exclude a plurality.Furthermore, it is to be noted that features or steps having beendescribed with reference to one of the above sample embodiments can alsobe used in combination with other features or steps of other embodimentsdescribed above. Reference numerals in the claims are not to beconstrued as limitations.

1. A level measuring instrument with a variable transmitting power formeasuring a filling level, comprising: a generator unit generating atransmit signal; and a controller controlling the generator unit;wherein the generator unit is configured for generating differenttransmitting powers of the transmit signal.
 2. The level measuringinstrument according to claim 1, wherein the generator unit comprises: afirst oscillator generating a first oscillator signal; and a secondoscillator generating a second oscillator signal; wherein the controlleris configured for selectively driving one of the first oscillator andthe second oscillator.
 3. The level measuring instrument according toclaim 1, further comprising: a tap tapping a reference signal from oneof the first oscillator signal and the second oscillator signal.
 4. Thelevel measuring instrument according to claim 1, further comprising: anattenuation element setting attenuation of the first oscillator signal.5. The level measuring instrument according to claim 4, wherein theattenuation element is configured as an attenuation mat to be adhered toa substrate.
 6. The level measuring instrument according to claim 4,wherein the attenuation element has a variable controllable attenuationand wherein the controller is configured for controlling the attenuationelement.
 7. The level measuring instrument according to claim 1, furthercomprising: a transmission amplifier setting amplification of the secondoscillator signal.
 8. The level measuring instrument according to any ofclaim 2, further comprising: a directional coupler including a firstinput, a second input, a first output and a second output; wherein thefirst input of the directional coupler is connected to the firstoscillator and the second input is connected to the second oscillator;wherein the first output of the directional coupler is the tap tappingthe reference signal, and wherein the second output is configured foroutputting the transmit signal; and wherein the directional coupler isconfigured for attenuating a signal, which is fed at the first input andoutput at the second output.
 9. The level measuring instrument accordingto claim 8, wherein the directional coupler is configured as one of anasymmetric hybrid coupler and a symmetric hybrid coupler.
 10. The levelmeasuring instrument according to claim 1, wherein the first and secondoscillator signals are electromagnetic signals; and wherein the levelmeasuring instrument is configured as a filling level radar.
 11. Thelevel measuring instrument according to claim 1, wherein the levelmeasuring instrument is configured as a pulse radar system.
 12. Thelevel measuring instrument according to claim 1, further comprising: areceiving unit determining the signal strength of a receive signal;wherein the controller is coupled to the receiving unit; and wherein thecontroller is configured so that the first transmitting power isgenerated when the signal strength of the receive signal exceeds athreshold value.
 13. The level measuring instrument according to claim12, wherein receipt, determination of signal strength, and comparisonwith the threshold value of the receive signal strength are performedautomatically.
 14. A generator unit according to claim 1, the generatorunit generating different transmitting powers of a transmit signal formeasuring a filling level.
 15. A method for measuring a filling level,comprising the steps of: controlling a generator unit for selectivelygenerating a first transmitting power of one of a transmit signal and asecond transmitting power of the transmit signal; and generating thetransmit signal selectively with one of the first transmitting power andthe second transmitting power.
 16. The method according to claim 15,further comprising the steps of: receiving a receive signal; determininga signal strength of the receive signal; and controlling the generatorunit so that the first transmitting power is generated when the signalstrength of the receive signal exceeds a threshold value.
 17. The methodaccording to claim 15, wherein the generator unit comprises a firstoscillator generating a first oscillator signal and a second oscillatorgenerating a second oscillator signal.
 18. The method according to claim15, wherein the generator unit controls one of a variable attenuationstage and a variable amplification stage depending on a defined signalstrength of the receive signal; and wherein only one oscillator isimplemented for generating the transmitting power.
 19. The methodaccording to claim 15, wherein the generator unit controls one of thevariable attenuation stage and the variable amplification stageindependently from the signal strength of the receive signal.